This specification relates to speech recognition and speech understanding systems. Speech recognition and speech processing systems are prevalent in many consumer electronic devices. Many of these electronic devices now utilize speech command processing techniques to invoke and perform particular operations. For example, a user device, such as a smart phone, can process speech commands to perform specified operations that include searching the web, setting an alarm, calling a particular person, and so on.
A user device uses a speech recognition processing system to recognize and process speech commands. A provider of the speech recognition and processing system develops parsing rules for various commands a user will speak. Upon a successful parse of a command input by a rule, the action is performed (or may be performed subject to user confirmation).
Users, however, can articulate commands for a particular action in many different ways. Thus, the provider of the speech recognition and processing system cannot anticipate beforehand all possible commands that will be received, and thus cannot generate all possible parsing rules beforehand. Accordingly, some commands may not parse for a particular action.